[Capsaicin-induced corneal epithelial changes in rats].

To elucidate the mechanisms by which corneal sensory denervation causes corneal epithelial disorders, we investigated corneal epithelial changes in rats injected with capsaicin, which is known to desensitize the primary sensory neurons. Neonatal rats were injected with capsaicin (100 mg/kg) or only the vehicle as a control on the 2nd day after birth. Corneas were excised after 7-28 days and subjected to gold chloride staining. 3H-thymidine autoradiography, or immunohistochemistry using anti-substance P (SP) antibody. The results indicated poor attachment of corneal epithelium, decreased corneal nerve ending density, decreased 3H-thymidine uptake by epithelial cells, and decreased expression of SP in the epithelial layer in rats injected with capsaicin compared with the control rats. This suggests that decreased proliferation of corneal epithelial cells associated with decreased SP as well as poor attachment of the epithelium is one of the causes of neuroparalytic keratopathy.